Carbon blacks are generally produced in a furnace-type reactor by pyrolyzing a hydrocarbon feedstock with hot combustion gases to produce combustion products containing particulate carbon black.
Carbon blacks may be utilized as pigments, fillers, reinforcing agents and for a variety of other applications. For example, carbon blacks are widely utilized as pigments in the formulation of ink compositions, paints and the like, wherein it is generally desirable to use a carbon black pigment which can be easily dispersed.
For example, newsink compositions are made in two stages. First the carbon black pigment and a dispersing vehicle, comprising resin, additives, and oil or solvent, are mixed to form a "premix" and then the premix is ground, for example, in a shot mill, to complete the dispersion of the carbon black in the ink composition. Dispersion of the carbon black pigment in the ink composition occurs during the formation of the premix and during the grinding of the premix. A carbon black pigment which is easy to disperse will allow an ink maker to produce an ink in a reduced period of time, which results in improved economy. For the above reasons, and others, it would be advantageous to produce an easily dispersible carbon black pigment.
It is also desirable to produce ink compositions which have reduced tendency to rub off the printed paper and onto the reader's hands, clothing and/or furniture. For example, it is generally desirable for newsinks, utilized in printing newspapers, to have little tendency to rub off. One way to reduce rub-off is to use a carbon black pigment with lower structure, i.e. a lower dibutyl phthalate adsorption number. Unfortunately, however, such carbon blacks are difficult to disperse. Therefore, there is a need for a carbon black which is easy to disperse and provides an ink composition with reduced rub-off. By means of the present invention, a carbon black having good rub-off properties but poor dispersibility can be modified to produce a treated carbon black having similar rub-off properties with improved dispersibility characteristics.
One method, as shown in the article entitled "The Dispersibility and Stability of Carbon Black in Media of Low Dielectric Constant. 1. Electrostatic and Steric Contributions to Colloidal Stability"; Pugh, Matsunaga and Fowkes; Colloids and Surfaces, 7 (1983) 183-207, of dispersing carbon black in an ink formulation is to add a dispersant into the oil or solvent with the carbon black. The presence of the dispersant in the oil or solvent increases the dispersibility of the carbon black.